Spark-plug



c. N. CLARK.

SPARK PLUG.

APPLICATION FILED Dsc. L5. 1919.

1,374,431 Patented Apr. 12, 1921.,

UNITED STATES CHARLIE N CLARK, OF MINNEAPOLS, MIINNESOTA, ASSIGNOR TO 0F MINNEAPOLIS, MINNESOTA.,

ANTN V'. GLSON,

SPARK-PLUGn Speccation of Letters Patent.

Patented Apr. is, i921.

Application led December 15; 19.19. Serial No. 345,015.

new and useful improvements in S ark- Plugs; and l do'hereby declare the fo lowing to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains yto make and use the same.

My invention has `for its object to provide an extremely simple and highly efiicient spark plug for internal combustion engines; and to such ends, generallystated, the invention consists of the novel devices and combinations of devices hereinafter described and dened in the claims.

The improved spark plug is illustrated in the accompanying drawings wherein like characters indicate like parts throughout the several views.

Referring to the drawings:

Figure 1 is an axial section of the spark plug, some of the parts being shown in full; and

Fig. 2 is a section on the line 2-2 of 5f the parts of the spark plug, the numeral 3 indicates the tubular shell or body having an externally threaded end 4 adapting it to be screwed into the cylinder head in the usual way. At its outer end, the shell is internally threaded at 5 and at its intermediate portion is provided with an internal shoulder 6.

The core 7 of .the plug is preferabl of porcelain, and somewhat outward o its inner end, it has an enlarged portion 8 that fits the interior of the shell 3. The numeral 9 indicates a gasket, preferably of the asbestes type,`interposed between the shoulder 6 of shell 3 and the opposing shoulder of the enlarged portion of the core 7. The numeral 10 indicates an annular gland that works with threaded engagement in the threaded portion 5 of the shell 3 and surrounds the outwardly extended portion of the core 7. The numeral 11 indicates a gasket interposed between the inner end of the gland 10 and the shoulder of the enlarged portion 8 of the core.

In spark plugs as commonly constructed, porcelain cores are employed, but these, in time, become soaked with oil and filled with carbon, so that the plugs are frequently short-circuited, and moreover, these porcelain cores are frequently cracked by heat, and the cracks being filled-with carbon short circuit the plug. y A

To obviate the above defects, I rovide the porcelain core with a glass bus ing,.pref erably of a tough, heat-tempered glass, and which bushing is interposed in such manner as to prevent short-circuiting of the plug, even if the porcelain core should become oil .soaked or cracked. r1`his glass bushing 12 is fitted loosely into the core 8, and cement 13 is filled in between the two. The bushing 12 and inner end portion of the core 8 are formed with alined axial passages 12a and 8a through which the axial electrode 14 is extended with very considerable clearance. The inner end of this axial electrode 14 cooperates with a grounded electrode 15 connected to the inner end of the shell 3.

The outer end of the axial electrode 14 is secured in the inner end of a threaded rod 16 that is extended through the bushing 12, and on the threaded outer end of which is a lock nut 17 and a clamping nut 18.

'The rod 16 may be anchored to the bushing 12, either by threaded engagement, or by cement, or both, and a cement plug 19 is also preferably placed in the bushing around the electrode 14 immediately adjacent to the inner end of the rod 16 to further anchor the said electrode 14 and to insure a gastight joint. The cement 13, of course, anchors the glass bushing 12 in the core 8.

As the axial electrode 14 is spaced from the inner portion of the core 8, short circuiting of the plug through the inner portion ot' the core is prevented, and the glass bushing` 12 cannot, of course be oil-soaked, and hence always afford' the best possible insulation between the outer portion of the electrode 14 and the inner portion o1l the rod 16 on the one hand, and the surrounding metal portions of theshell 3 and gland 10 on the other hand.

This plug, while of simple construction and easily made at comparatively small cost, is strong, durable and efficient for the purposes had in view.

lVhat I claim is:

1. In a spark plug, the combination with a tubular metallic shell, of a porcelain core extended into and anchored to said shell, a tubular glass bushing extended axially within said core and anchored therein, a metallic rod extended into and anchored to the outer portion of said core, and an axial electrode anchored to said rod extended axially therefrom through the inner portion of said glass bushing andthrough said core to the inner end of said shell, said axial electrode being spaced from the surrounding walls o f said Core bushing and shell, and a grounded electrode applied to the inner end of said shell for cooperation with the inner end of said axial electrode.

2. ln a spark' plug, the combination with a tubular metallic shell and anannular gland working with threaded engagement in the outer end thereof, of a porcelain core extended into said shell and having an enlarged portion clamped between said shell and gland, a tubular glass bushing extended axially within said core but terminating short of the inner end thereof, a metallic rod anchored in said bushing, an axial electrode extended from said rod through the inner ends of said bushing and core, said inner portions of the bushing and core being` yspaced from-said axial electrode, and a grounded electrode applied to the inner end of said shell.

3. 'In a spark plug, the combination with a tubular metallic shell vand an annular gland working with threaded engagement in the outer end thereof, of a porcelain core extend*- ed into said shell and having an enlarged portion clamped between said shell and gland, a tubular glass bushing extended axially within'said core but terminating short of the inner end thereof, a metallic: rod anchored in said bushing, an axial electrode extended from said rod through the inner ends of said bushing and core, said inner portions of the bushing and core being spaced from said axial electrode7 a grounded electrode applied to the.inner end of said shell, cement interposed between said bushing and core, and a cement block in said bushing surrounding said axial electrode immediately adjacent to the inner end of said metal rod.

n testimony whereof l aiix my signature.

CHARLIE N. CLARK. 

